In recent years, a flash device has been widely employed to an optical apparatus such as, for example, a camera. Particularly when the flash device is employed to the photographing, the light exposure is the most important component. In an automatic light adjusting device which is employed to the photographing the flash light is ceased, when the reflected light from an object to be photographed attains to a predetermined value.
The reflected light from the object to be photographed is, however, few in case that color of the object is black or in case that distance from the object to be photographed to the flash device is long, and the reflected light quantity is, therefore, few. By the few reflected light quantity, the automatic light adjusting device was inactivated, and thereby a photographer could not judge easily how to adjust the distance between the object to be photographed and the flash device or to adjust the diaphragm. To contrary, when the color of the object to be photographed is white, the reflected light quantity becomes much or the distance from the object to the flash device is very small, the reflected light quantity becomes large, and, accordingly, the automatic light adjusting device does not activate correctly. It is also impossible for the photographer how to alternate the distance or to adjust the diaphragm.